Electric demand meter



Feb. 17. 1925. 1,526,727

A.' J. TWOGOOD ELECTRIC DEMAND METER Filed May 7,

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Feb. 17. 1925.

- J. TWOGOQD ELECTRIC DEMAND METER A. J. TWOGOOD ELECTRIC DEMAND METER Filqd May v, 1917 3 Sheet s-Sheet s I gnbmfloc Md 72 070 0 a;

Patented Feb. 17, 1925.

ARCHIE J. TWOGOOD, OF BERKELEY, CALIFORNIA.

ELECTRIC DEMAND METER.

Application filed May 7, 1917. Serial No, 167,024.

To all whom it may concern.

Be it known that I, Anornn J. Twocoon, a citizen of the United States, residing at Berkeley, in the county of Alameda, State of California, have invented certain new and useful Improvements in Electric Demand Meters; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The present invention relates to electric meters, and more particularly to that class of meters commonly employed for registering the demand made by an electrical installation upon the source of supply there for, and commonly known as demand meters.

The primary object of the invention is to provide an improved construction of demand meter that will indicate in watt hours, the demand for a specific time interval immediately preceding the time of indication, and for overlapping intervals.

The object of the invention is to provide a device of this character which is adapted for operation in combination with the common form of watt hour meter.

Referring to the drawings,

Figure 1, is a front elevational view of the device, the casing being shown in section,

Figure 2, is a side elevation partly in section taken on line 2-2 of Figure 1,

Figure 3, is a diagrammatic View of the meter system.

Figure 4, is a detailed sectional view of the register.

Figure 5, is a top plan View showing the method of securing the contacts of the drum,

Figure 6, is a detailed view of a portion of the drum,

Figure 7, is a sectional view on the line 7-7 of Figure 6,

Figure 8, is a detailed sectional view on the line 88 of Figure 1,

Figure 9, is a detailed sectional view of the contact member 49; and, V

Figure 10, is a detailed sectional view of the solenoid 56.

Referring more particularly to the drawings, the reference character designates the disc of a watt hour meter, and connected thereto, centrally thereof is the vertically extending shaft 16 upon the upper end of which is secured a worm gear 17. The. casing is designated by the reference character 18 and secured to one of the side walls thereof is a bracket 19 which is provided with two pairs of arms 20 and 21, and mounted in the arms 21 is a shaft 22 on which is mounted a. worm gear 23 which meshes with the worm 17 of the shaft 16.

Mounted in the arms 20 is the shaft 26, on which is fixed a gear wheel 24 which meshes with the gear wheel 25 secured to the shaft 22in spaced relation to the gear Wheel 23, and fixed also on the shaft 26 is a cam member 27 which rotates with the gear Wheel 24. Extending from the rear wall of the casing 18 are brackets 28 and mounted for rotation in said brackets 28 is a drum 30 the specific construction of which will be hereinafter set forth.

Projecting from the rear wall of the cats ing 18 is a guide member 29 having upper and lower openings 31. Slidably mounted in the lower opening of said guide is a rod 32 the inner end 33 of which contacts with the surface of the cam 27. The other end of the member 321s provided with right angular extensions 34 and 35, and connected in an eye 36 carried by the right angular extension 34 is a coil spring 37 the other end of which is secured at 38 to the rear wall of the casing. The upper end of the right angular extension is beveled as at 39, and projecting from the right angular extension 35 from a point near its beveled end 39 is a lateral arm 40 which is parallel to the rod 32 and projects transversely of the periphery of'the drum 30. Rigidly carried by the member 40 are downward converging guides 41 the upper ends 42 of which are arranged in wide spaced relation as shown in Figure 1, for a purpose to be hereinafter described. a

The rear wall of the casing 18 is provided with a guide 43. Slidably mounted in the upper opening of the guide 29 is a rod 44 from which extends an upright 45 of approximately one-half the length of the rod 32 having at the upper end a lateral arm 48 slidable in the guide 43, and extending in parallel relation to the rod 44 but from the opposite side of the upright 45. The end of the arm 48 is extended upwardly, as shown at 49. In the extremity of the portion 49 is a recess 50 in which is received a contact ball 51 that is held yieldably projected partway therefrom by a helical spring 53.

i The upright 45 is provided with two spaced brackets 54 and 55, and mounted between said brackets and rigidly carried by the bracket 55 is asolenoid 56 the ends of the core 57 of which extends through the brackets 54 and 55 and through a guide member 58 rigidlysecured as at 59 to the upright 45, and extending at right angles therefrom. The core 57 is provided near its upper end with a plate or washer 80 which is rigidly secured thereto, and encircling the upper portion of the core between the upper face or said plate or washer 60 and the under face or" the bracket 54 is a coil spring 61. An eye member 62 is formed upon the upright 45and connected thereto is a coilspring 63 the other end of which is connected as at 64 to the casing 18.

Slidably mounted in the guide 58 is a latch rod 65, one end of which projects from said guide and has an upwardly directed lug 66 extendingabove the guide, to which is connected a coil spring 67, the other end of said spring being connected to the guide.

58. The outer or free end of the rod is rebent into hook form as shown at 65-tor engagement with the end 39 of the upright 35.

Depending from the arm 48 is a bracket 70 and pivotally mounted in said bracket is a contact lever71. One end-of the lever 71 projects over the core 57 of the solenoid 56 and is inthe path of travel of the upper end of said core while the other end carries a contact 72. Projecting "from the bracket 70 is a lug 74 having a contact 75. The purpose of these contact members will be hereinafter set forth.

By reference to Figures 6 and 7, it will be seen that the periphery of the drum 30 is provided witha plurality of contact members which are adapted to slide transversely or the periphery of the drum. The periphery of the drum is provided with a plurality of 1 transversely extending and regularly spaced parallel metal contact plates 81 arranged in pairs, the plates of each pair being retained in spaced relation, and insulated tromthe plates of each of the adjacent pairs by means of mica or other insulating strips 82. The contact members 81 arenotched as at 83 and 84, the notches receiving the peripheral edges of the drum 30, and the notches 83 receiving an annular ring 85 which is secured in place by means of a band or the like 86 the free ends of which are secured together as at 8?.

The inner end 01'. each of the contact members 80 is preferably square o as at 88, said squared portion 88 being provided with notches 89 and 90 in which is adapted to eat a spring member 91 which as shown in Figure 5 has its ends bifurcated to provide a depending intermediate resilient finger 92 and two spaced resilient fingers 93, the resilient fingers 92lying between thebrass contact strips 81, while the two resilient fingers 93 contact with the lower edge faces of said contact strips 81 as best shown in Figure. 7. By this construction it is clearly apparent that the contact members 80 are free to move transversely of the periphery of the drum 80 upon their engagement with the diverging guides 41.

The transversely extending brass contact strips 81 are of the same length as the mica strips 82 and as shown at 95 in Figure 2, their free ends are exposed to form a commutator or the like, and mounted stationary with respect to the drum 30 is a block 96 of insulating material, and to the opposite ends of said block, brushes 97 and 98 are secured. The brush 98 is shorter in length than the brush 9? and by this construction it is apparent that the brushes 9? and 98 will engage the ends of adjacent pairs of contact strips 81.

As shown in Figure 2 a bracket 100 projects from the rear wall of the casing 18, and supported by said bracket and overlying the drum 30 and extending beyond the said drum to the right asufficient distance is a resistance member 101.

The resistance member 101 comprises two resistance elements arranged in series, one of said elements being wound as a non-inductive coil not shown in the drawings. The resistance element shown is also non-inductive.

Referring to Figure 8 it will be seen that this resistance element comprises a base 102 and connected to said base is a plurality of fiber strips 103'. Secured to the base 102 at the lower end thereof is a metallic holder 104, and packed in said holder is a plurality of laminations 105, constituting contact elements these laminations being formed from brass or other metal which is rolled very thin and being separatet by paper or other insulation. These laminations are rigidly held in position in holder 104, from which they are insulated. lVound upon the fiber strips 103 are the sections of resista-m e wire 104, and as shown in Figure 8 this wire is tapped off at intervals and the taps secured to the lamination terminals 105.

The gear carried by the shaft 111 meshes with gear 112 carried on the shaft of the drum 30. The shaft 111 is operated by means of a spring motor 111 or the like which is adapted to drive the drum at such a constant speed that the time which elapses between the leaving of one of the contacts 80 from the converging ends of the guides 41 and the time at which said contact 80 engages the laminations 105 is equivalent to the period over which the demand is desired.

The cam; member 27 is rotated "from the watt-hour met r disc 15 by means oi a sha it 16, worm gear 17, shaft 22, and the pinions 23, 24, and 25, As the cam 27 is rotated it will be seen that the adjacent ends Hit) and 44 of the rods 32 and 44 will bear against the peripheral face thereof under the influence of the coil springs 37 and 63 respectively. As this cam revolves in the direction of the arrow A in Figure 1, it will be seen that the arms 32 and 44 will be moved to the right in Figure 1, and owing to the fact that the contact ball 51 is in a direct line with the space between the lower spaced ends 42 of the convergent guide members 41, said contact 51 and spaced ends 42 will move in unison in the same direction and parallel with the axis of the drum 30 upon rotation of the cam. Upon continued rotation of the cam the point X of the cam passes the engaged end of the rod 32, and under the influence of the spring 37 the rod 32 is moved to the left in Figure 1, thus moving the guide members 41 to the left. Owing to the fact that the free end 44 of the rod 44 is still. in engagement with the outer portion of the periphery of the cam 27, the rod 44 is prevented from movement, and upon movement to the left of rod 32 until it engages the point Y of the cam 27, the beveled face 39 of the extension 35 engages the lower projecting end of the solenoid core 57 and elevates the same to permit the member 35 to pass to the left thereof. By this time the end 44 of the rod 44 has been released from engagement with the point X of the cam 27, but owing to the engagement of the end 39 of the extension 35 with the left hand side of the lower end of the solenoid core 57 the rod 44 is prevented from move ment toward the left in spite of the influence exerted by the spring '63 and this end 44 does not move to the point Y of the cam 27 Upon further rotation of the cam 27 the rod 32 is again moved to the right in Figure 1 and owing to the engagement of the beveled end 39 of the extension 35 with the solenoid core 57 the member 44 is moved to the right in Figure 1 thus moving the contact member 51 across the lamina tions 105 of resistance element 101, and the guides 41 transversely of the periphery of the drum 30.

The cam, actuated by the watt-hour meter, is preferably designed for operation under normal or average load conditions so as to make one revolution during a multiple of the period of rotation of the drum which operates at a constant speed and under accurately timed conditions. For example, the cam is adapted under normal load or demand conditions to make one revolution in thirty minutes, variable however, obviously, by variations of demand by which its speed is directly controlled, while the drum makes one complete revolution in fifteen min t s t' a h re l t on o the ca e;

therefore, of which the speed is proportional to the demand, the guides 41 are carried more or less slowly across the face of the drum toward the right and then suddenly return, thus leaving at the extreme right of the drum the contact which escaped from 42 just before the rod 32 escaped from the point Y of the cam 27, while at the same time the convergent ends of the guides carry the immediately following contact to the extreme left of the drum. (See dotted lines in Fig. 1).

These momentarily or abruptly separated contacts 80, which have been adjacent to each other throughout the preceding movement of the drum, in due course of operation, fifteen minutes, or other time intervals, make simultaneous contact with remote laminations or contact elements 105 of the resistance 101, and at the same instant that the ends of the contact element 81 corresponding with said engaged contacts 80 are contacted by the brushes 97, 98, which are included in the circuit of solenoid 56. The strength of the current in said solenoid, and hence its pull, is at all times determined by the amount of resistance included between one of the contacts 80 and the contact 50, provided two adjacent contact members 80 are simultaneously in contact bot-h with the brushes 97, 98 and laminations 105 of the resistance or rheostat. This current strength in the solenoid 56, due to the voltage impressed thereon, is approximately onehalf that of the constant voltage impressed on the resistance. Therefore, the only time at which the potential of the current passing through two adjacent contacts 80 will be high enough to energize the solenoid 56, will be when the adjacent contacts 80 are separated a distance equal to the width of the drum 80. Thus the separated contacts 80 will touch the laminations 105 at widely separated points, which will be practically one-half of the length of the resistance, The energization of solenoid 56 raises its core to disengage it from the end 39 and engage and raise the adjacent end 73 of the switch to break the circuit at 72'5 and through solenoid 120, while at the same time the latch 65 moves to the left, under the influence of the spring 68, to dispose its inner end beneath the end of the solenoid core 57 to hold it elevated until released by the subsequent withdrawal of said latch by the engagement of the end 39 with the hook 65, upon return movement of the member 44 to the left.-

This operation permits the rod 44 to move toward the point Y of the cam 2-7, It: is therefore evident that the rod 44 moves to ward the left, distance equal to X-Y or equal to the distance between the two contacts 80 before mentioned as being of maximum distance apart. T his movement ot the member 4-4 however is later than the movement of the rod 32 by a space of time equal to the interval of the meter, because the interval must elapse before the contacts separated by the width of the drum are placed in contact with the brushes 9? and 98, and therefore contact 50 makes its proportional distance from the contact 80 in. contact with the resistance 101 and the brush 9? which distance represents the energy consumed during the elapsed time interval of the me ter. A sourre oi constant potential is supplied to the resistance 101 through the leads :1. Should the came 27 cease to turn at the time the member 32 engages the point Y of the cam 27, the meter would fail to record correctly, after the time interval had elapsed, for the reason that the arm 1 1 would be prevented from movement to the left by that portion of the cam still under 11.

In this connection it will be understood that, in spite of the fact that the cam is stationary, the drum continues to rotate at its normal rate of speed, but with the result that all of the contacts 80, which pass out from between the convergent ends of the guides a l, will be arranged in a straight line peripherally of the drum, and at the left-hand side thereof. Under these conditions, and when the drum has rotated to bring the separated contacts 80 into engagement with the laminations 105, the solenoid 56 will be energized, as before, raising its core 5? upwardly, and thereby permitting the latch rod (35 to pass therebeneath, holding the core out of the path of the end 39, and maintaining the circuit through. the contacts 7275, broken. Thus the circuit to solenoid 120 is broken during the time that the included resistance of 1.01 is in excess of an amount proportional to the demand for the interval precedin that is when the contact is half way or more across the resistance and contact 80 is touching 1.01 at the left end. This must obtain until arm 14 is allowed to move to the left a distance X-Y by a slight rotation of cam 27. When the cam is again moved, as the meter begins to register, the arm of rod 44-, being free from the arm 32, will immediately move inwardly to the point Y, of the cams surface, carrying point 50 again into alignment with converging ends 11, it will maintain its proper relation with respect to the contact 80 left, the time interval previous at the left end of the drum, and again closing points '12 and 75, and thus permit both the arm 4- 1 and the arm 32 to be moved toward the right, by the cam, carrying the guide arms 11 across the face of the drum. As the rod 1 1 moves toward the left the hook will engage with the end 39, with the result that the latch rod 65 will be withdrawn from beneath the core 57, so

that as the next complete rotation of the cam ends, and the rod 32 leaves the point X, the end 39 will again engage with the lower end of the said core, lor moven'ient of the arm 41-, and its associated parts, toward the right, in the normal operation of the mechanism. Furthermore, as the arm or rod it moves toward the left, under the conditions above mentioned, the contact 50 is moved toward the left-hand end of the resistance 101, so that its position, with rcspect to the left-hand contact will be such that the voltage between this contact 80 and 51 will be proportional to the demand. By reference to 1* igures $5 and 4, it will be seen that the registering instrument consists of the solenoid 120 and 121 in which is slidably mounted a core 122, said core having intermediate its ends a rack 123, which meshes with a pinion 12st, carried by the indicator pointer 125. Pointer 125 is rigidly connected with pinion 12 1, While pointer 127, mounted concentrically with pointer 125, is free to turn, but is held in position by trict-ional resistance until moved forward by pointer 125 striking a l ug 123, mounted on pointer 12?, and upon retraction of pointer 125, pointer 127 remains in forward position and thereby indicates the foremost position of pointer 125, or the maximum reading of the instrument.

ith the parts in position shown in Figures 1 and 3 it will be seen that the lever 71 and lug 74 complete a circuit through the wire 128, through the solenoid 120, wire 129 to the brush 9?, thence to the contact 80, a lamination 105, portion of resistance 101, another lamination 105, contact 51 and wire 13 to the lug 74, energizing the solenoid 120 and moving its core 122 against the action of a spring 131 and the influence of solenoid 121 to move the members 125 and 127 to make the indication. The solenoid 120 is energized proportionally to the dif fernce in potential between the contact members 50 and 80 on the resistance 101 thus to move the core 122. One of the functions oi the registering instrument is to compensate for variation in line voltage impressed upon the resistance element 101. This accomplished by means of the compensating solenoid 121. It is therefore evident from the foregoing that the pointer 125 a lways indicates the average demand over the immediately elapsed time interval.

The principle of the indicator or register is to measure, not the volt-age between 80 and 50 in contact with the resistance member, but the ratio of this voltage to the impressed voltage indicated at 101 in Fig. 3. This ratio must be proportional to the distance 8050, for reasons explained, and this ratio is proportional to the energy consumed during the past interval or period of time.

The function of the solenoid 56, and the accompanying parts, is merely to permit the use of a drum of limited length, so that relative positions of contacts 80 and 50, touching laminations 105, may be periodically (i. e. at each revolution of cam 27) returned to the left portion of the drum surface. Ex-

cept for this it would be necessary to con-' tinue motionot the arms and contacts indefinitely to the right, thus requiring a drum and resistance element of impracticable lengths.

Having thus described the invention, what is claimed, is:

1. In an electric demand meter, the combination with a watt meter, of a resistance for connection across the circuit in which the demand is to be measured, a contact adapted to traverse the resistance and operably connected with the watt meter, a second contact having means for moving it at a variable rate across the resistance, and a register in circuit between the contacts.

2. An electric demand meter comprising a resistance for connection across a circuit in which the demand is to be measured, a pair of contacts movable independently of each other across the resistance, means responsive to the demand and connected with one of the contacts for moving it across the resistance at a speed variable or constant, in accordance with the demand, a second contact disposed to traverse the resistance and having means for moving it at a variable speed across the resistance, and aregister having an operating coil in circuit between the contacts and having a retarding coil for connection in multiple with the resistance.

3. An electric demand meter comprising a resistance for connection across the circuit in which demand is to be measured, a multiplicity of contacts having means for bringing them successively into circuit with the resistance at equal intervals, a second contact disposed to traverse the resistance, a watt meter under the influence of which the second contact is movable, and a demand register responsive to the difference in potential between the points of resistance with which are in circuit the last named contact and the contact of the first named series, brought into circuit with the resistance.

a. An electric demand meter comprising a resistance for connection across the circuit in which demand is to be measured, a multiplicity of contacts, means for bringing them successively into circuit with the resistance at equal intervals, and means responsive to the power in the circuit cooperating with said first means for causing the points of contact of successive contacts to progress across the resistance at a rate proportional to said power a predetermined time interval previous, a second contact disposed to traverse the resistance, a watt hour meter under the influence of which the second contact is movable, and ademand register responsive to the difference in potential between the points of resistance with which are in circuit the last-named contact and the contact of the first-named series, brought into circuit with the resistance.

5. An electric demand meter comprising a resistance for connection across a circuit in which demand is to be measured, a contact disposed to traverse the resistance with means for moving it at a speed proportional to the power in the circuit, a multiplicity of contacts, responsive to the power in the circuit for causing the points of contact of successive contacts to progress across the resistance at a rate proportional to said power at a predetermined interval of time before, the relation between the first-named contact and the contact of the last-named series brought into circuit with the resistance between them being proportional to the energy consumed in said circuit to be measured, during the predetermined time interval immediately preceding, in combination with a demand register responsive to the difference in potential between said contacts in circuit with the resistance.

In testimony whereof I aifix my signature in the presence of two witnesses.

ARCHIE J. TVVOGOOD.

Witnesses:

RALPH S. Twoeoon, ELLIS E. France. 

